Drought evolution and driving mechanisms in the China-Pakistan economic corridor under a changing environment

Study region: The China-Pakistan Economic Corridor (CPEC) is a critical hub of the ''Belt and Road'' initiative, making it particularly vulnerable to drought effects driven by climate change and human activities. Study focus: This study evaluates the Standardized Precipitation Evapotranspiration Index (SPEI) and the Soil Moisture Deficit Index (SMDI) at 0–10 cm and 10–40 cm depths using monthly grid data for meteorological and soil moisture from 1981 to 2021. The Run Theory, principal component analysis, and other methodologies were employed to analyze drought evolution and its driving factors. New hydrological insights for the region: The longer the timescale, the stronger the correlation between SPEI and SMDI. ''Dryness-dryness,'' indicating prolonged low moisture, and ''dryness-wetness,'' marking transitions to wetter conditions, were recorded during 1998–2003 and 2016–2021, respectively. Spatial trend analysis revealed significant declines in SPEI during summer and winter, while SMDI showed an upward trend in the northeast and southwest regions of CPEC. As indicated by the SPEI, SMDI0–10, and SMDI10–40, extreme drought events occurred with respective counts of 10, 8, and 6. These significant drought events primarily affected Sindh, Punjab, and Gilgit-Baltistan. The study identifies strong correlations (r > 0.7) between drought indices and climate factors, with atmosphere status exerting the more significant impact on drought in CPEC. These insights are invaluable for formulating effective drought monitoring and early warning systems within the CPEC region.